Hot water process

ABSTRACT

THE SPECIFICATION DISCLOSES A METHOD OF DETERMINING THE PROCESSABILITY OF BITUMINOUS TAR SANDS AND REGULATING THE AMOUNT OF WATER MIXED WITH TAR SANDS IN A HOT WATER PROCESS ACCORDING TO THE DETERMINED EASE OF PROCESSABILITY OF THE SANDS. BY THE INVENTION THE ALUMINUM CONTENT OF THE SANDS IS DETERMINED AND RELATED TO THE CLAY CONTENT OF THE SANDS. THE SANDS CLAY CONTENT IS USED AS A VARIABLE FOR DETERMINING THE AMOUNT OF WATER AND REAGENT TO BE MIXED WITH THE SANDS IN THE HOT WATER PROCESS.

c. N- WHITE ET AL HOT WATER PROCESS Filed m 9. 1968 Jan. 26, 1971DILUE'NT FROTH\ l5 WATER AND STEAM -2s SETTLER 2a; 'SCAVENGER FROTH\SEPARATION" n .AIR

ZONE MIDDLINGS FLOTATION A 'SCAVENGER 27- zone OIL-LEAN moounes SAND,TAILINGS 2 --ISPECTROME'I'JER \NEUTRON IRRADIATION ZONE BITUMINOUS TARSANDS mveu'rons CHESTER N. WHITE ismon VLAND TVz 9 United States Patent3,558,469 HOT WATER PROCESS Chester N. White, Moylan, and Junior WestLoveland, Media, Pa., assignors to Great Canadian Oil Sands Limited,Toronto, Canada, a corporation of Canada Filed July 9, 1968, Ser. No.743,500 Int. Cl. C10q 1/04 US. Cl. 208-11 10 Claims ABSTRACT OF THEDISCLOSURE This invention relates to a method for determining theprocessability of bituminous tar sands. Specifically the inventionrelates to an improved hot water process for separating bitumin from tarsands.

Deposits of tar sands exist at various places throughout the world. Themost extensive deposits are found in northern Alberta, Canada. Thedeposits are of Mesozoic Age. They underlie truncated Paleosoiclimestones and are usually overlain by Pleistocene sediments. Thedeposits underlay more than 13,000 square miles at depths of 0 to 2000feet. Total recoverable reserves of oil from the deposits afterextraction and processing are estimated at more than 300 billionbarrels.

The sands are composed of a siliceous material, generally having a sizegreater than that passing a 325 mesh screen, saturated with a relativelyheavy, viscous bitumen in quantities of from 5 to 21 weight percent ofthe total composition. More typically, the bitumen content of the sandsis about 8 to 15 percent. This bitumen is quite viscous and containstypically 4.5 percent sulfur and 38 percent aromatics. Its specificgravity at 60 F. ranges typically from about 1.00 to about 1.06. The tarsands also contain clay and silt in quantities of from 1 to 50 weightpercent of the total composition. Silt is normally defined as mineralwhich will pass a 325 mesh screen but which is larger than 2 microns.Clay is mineral smaller than 2 microns including some siliceous materialof that size.

There are several well-known processes for effecting the separation ofbitumen from the tar sands. In the so-called cold water method, theseparation is accomplished by mixing the sands with a solvent capable ofdissolving the bitumen constituent. The mixture is then introduced intoa large volume of water, water with a surface agent added, or a solutionof a neutral salt in water. The combined mass is then subjected to apressure or gravity separation.

In the hot water method, the bituminous sands are jetted with steam andmulled with a minor amount of hot water at temperatures in the range of140 F. to 210 F. The resulting pulp is dropped into a stream ofcirculating hot water and carried to a separation cell maintained at atemperature of about 150 to 200 F. In the separation cell, sand settlesto the bottom as tailings and bitumen rises to the top in the form of abitumen froth. An aqueous middlings layer containing some mineral andbitumen is formed between these layers. A scavenger step may beconducted on the middlings layer from the primary separation step torecover additional amounts of bitumen therefrom. This step usuallycomprises aerating the middlings as taught by K. A. Clark, The Hot WaterWashing Method, Canadian Oil and Gas Industries 3, 46 (1950). The frothscan be combined, diluted with naphtha and centrifuged to remove morewater and residual mineral. The naphtha is then distilled off and thebitumen is coked to a high quality crude suitable for furtherprocessing. The hot water process is described in detail in UnitedStates patent application Ser. No. 509,589, Floyd et al., now Pat. No.3,401,110.

Several techniques can be used for the mining of the tar sands. Depositsat or near the surface can be mined by open-pit mining techniques inwhich overburden, if any, is stripped away and the exposed sands minedby conventional digging equipment. Preferably the mining is by giantbucketwheel excavators which have been found to be extremely useful inthis application. The mined material is then transferred to theprocessing area for separation of the bitumen.

The ease with which the bitumen is separated from the tar sands variesconsiderably through a deposit. Some sands result in high yields whileothers, from the same deposit, give low primary bitumen froth yields inthe hot water process. This ease of processability is related to thefines content of the tar sands as described by Floyd et al. in UnitedStates patent application 509,589. Floyd et 211. point out that if clayand silt are allowed to build up in the separation cell of the hot waterprocess, the viscosity of the cell middlings layer will increase. Con-,currently with such increase, an increase in the proportions of bothbitumen and sand retained by the middlings will occur. If the clay andsilt content is allowed to build up too high in the system, effectiveseparation will no longer occur and the process will become inoperative.Floyd et al, propose regulating the recycling and withdrawal ofmiddlings and input of fresh water to avoid inoperativeness. In Floyd etal., middlings viscosity and/ or density is measured and input of freshWater determined thereby. It is proposed by the present invention todetermine the fines content of the tar sands to their introduction tothe hot water process and to regulate the fresh water input into theprocess according to the measured fines content of the sands so as toprovide a constant anticipatory control on middlings viscosity. By thepresent invention the middlings viscosity can be controlled andmaintained in the desired range of about 0.4 to 5.7 centipoise.

United States Pat. 3,273,967, Wilson, teaches a method for determiningthe processability of tar sands which comprises analyzing samples fortheir content of a member selected from the group consisting of iron andzinc, and correlating the analyses with the sample to determine thelocation of the more easily processable tar sand. The patent teachesthat zinc and iron and particularly iron are the only elements whichappear to vary to any extent so as to give an indication of theprocessability of the tar sands. In contrast to this teaching thepresent invention measures the aluminum content of the sands todetermine their processability. It has been found that the aluminumcontent of the sands is a more accurate indicator of processability thanthe iron or zinc contentthe more easily processable sands having thelower aluminum contents and the more difficulty processable sands havinghigher aluminum contents. The aluminum content of the tar sands isdirectly related to the fines content of the tar sands so that a measureof the sands aluminum content is proportional to the sands fines contentand is therefore a measure of ease of processability. On the other handit is thought that iron or zinc contents are merely incidentallyvariable with ease of processabilitythe iron or zinc content beinggenerally low when sands aluminum content is high. A determination ofthe aluminum content, however, is a more reliable indicator ofprocessability because it is a direct measurement of the fines content.On the other hand, iron or zinc content in some sands can be high whenfines content of the sands is high so that in this case the iron or zinccontent are not indicative of the processability of the tar sands.Furthermore all clay minerals contain aluminum but they may or may notcontain iron. In other words the iron and Zinc contents of tar sands arenot necessarily relatable to ease of processability.

The present invention can be described as an improvement to the hotwater process wherein the hot water process comprises forming a mixtureof water and tar sands, passing the mixture to a process separation zoneto form an upper bitumen froth layer, a lower sand tailings layer and amiddlings layer comprising water, mineral and bitumen and separatelyremoving the layers from the separation zone. The improvement comprisesdetermining the aluminum content of the tar sands and regulating theamount of water used to form the mixture of sands and water byincreasing the amount of water with higher aluminum content anddecreasing the amount of water with lower aluminum content so thatoptimum conditions are maintained for forming bitumen froth in theprocess separation zone. The determination of the aluminum contentallows for an anticipatory control of the proper amount of water used toform the water and sands mixture.

In the hot water process, monovalent alkaline reagents are added to thetar sands conditioning drum usually in the amount of 0.1 to 3.0 poundsper ton of tar sand. The amount of such alkaline reagent preferably isregulated to maintain the pH of the middlings in the separator zone ofthe process within the range of 7.5 to 9.0. Best results seem to beobtained at a pH value of 8.0 to 8.5. The amount of the alkaline reagentthat needs to be added to maintain a pH value in this range of 7.5 to9.0 varies from time to time as the composition of the tar sands fromthe mine site varies. Thus as the fines content of the sands increases,reagent consumption is increased. The present invention can provide aconvenient control of added reagent. By the present invention the tarsands aluminum content can be measured and clay content determined. Theamount of added reagent is then determined and added in anticipation ofpH change in the separation cell brought about by increased reagentconsumption with tar sands of varying clay contents as determined bymeasured aluminum content. Thus a more delicate control can bemaintained over the process resulting in a savings in reagent and themaintenance of a continuous optimum bitumen froth yield. Thus by theprocess of the present invention, water input into the hot waterprocess, reagent addition and both water input and reagent addition canbe controlled according to the determined processability of the tarsands feed.

Another embodiment of the present invention relates to the means used todetermine the aluminum content of the tar sands. It has been found inthe present invention that aluminum content of tar sands can bedetermined by rendering the tar sands or a portion of feed sandsradioactive by neutron irradiation, recording emissions from the sandsand analyzing the emissions to determine aluminum content and hence theclay content and ease of processability of the sands.

In one preferred embodiment, a neutron irradiation system, deuteriumgas, is ionized and accelerated in a beam which is directed against atritium target to produce fast neutrons. The neutrons are directedagainst the tar sands to cause them to become artificially radioactive.The gamma rays emitted by the radioactive sands have energiescharacteristic of the elements that emit them. Analyses of theseemissions at various energy levels provide an energy spectrumcharacteristic of the elements present and proportional to the amount ofthe elements, thus permitting a quantitative analysis of the sands. Notonly does this procedure allow determination of aluminum Cir content butalso silicon content, oxygen and carbon as well. The aluminummeasurement provides a continuous measure of clay content and providesoperators of hot Water separation processes with an anticipatoryindication of quantities of monovalent alkaline reagents and waterneeded to properly treat the bituminous tar sands to obtain maximumprimary bitumen froth yield.

The invention will be described in more detail with reference to thedrawing which shows a preferred embodiment of the present invention andschematically illustrates controlling the fresh water input to a hotwater process for the separation of tar sands. In the drawing tar sandsare charged into the process from the mining area via line 1. The sandsor a portion of the feed sands pass preferably on a conveyor beltthrough the tar sands analysis zone 2 where the aluminum content of thesands is determined and the water feeds of the process are variedaccording to this determination as will be described in greater detailinfra. The tar sands analysis zone can comprise means useful fordetermining the aluminum content of the tar sands but preferably thezone consists of the neutron irradiation system as shown and describedsupra. With this type of system the conveyor carrying the tar sandsmoves the sands material past a leveling bar and under avertically-mounted neutron generator. The neutron flux from thisgenerator is incident upon the moving tar sands and causes fast neutroninelastic scattering from the carbon and oxygen atoms and activatesother elements such as silicon and aluminum. The prompt gamma raysemitted by the carbon and oxygen atoms in the sands are measured with aprompt gamma ray spectrometer at the point of irradiation while thedelayed activity due to silicon and aluminum is measured downstreambefore the sands are fed into the conditioning drum 4. A dataacquisition and analysis system is used consisting of an automated kv.neutron generator, a neutron monitor, a prompt gamma ray spectrometer, adelayed gamma ray spectrometer, and a data analysis unit. The neutrongenerator is positioned with the target assembly approximately /2 inchabove the plane of the sands. The nuclear analysis system is capable ofmeasuring the yield of two elements each from the prompt and from thedelayed gamma ray radiation from an irradiated material. The countingyields from each element measured are recorded by scalers which correctfor background radiation and Compton gamma rays from higher energy gammaradiation. The neutron flux, which is held at a constant level throughservo-controls in the generator control circuit, is also recorded on ascaler. At the end of a preselected counting interval the outputs of thefive scalers, the 24-hour time, and the elapsed time are printed and thesystem reset for the next count by action of the data analysis controlcircuit.

The tar sands pass on the conveyor illustrated by line 3 from theanalysis zone 2 to the tar sands conditioning drum 4. Water and steamare introduced into the conditioning drum from 5 and mixed with thesands. Enough steam is introduced to raise the temperature in theconditioning drum to above F. Monovalent alkaline reagent can also beadded to the conditioning drum to maintain the pH of the middlings layerin separator zone 14 within the range of 7.5 to 9.0. Mulling of the tarsands produces a pulp which then passes from the conditioning drum asindicated by line 6 to a screen indicated at 7. The purpose of screen 7is to remove from the tar sand pulp any debris, rocks, or oversizedlumps as indicated generally at 8.

The pulp then passes from screen 7 as indicated by 9 to a sump 10 whereit is diluted with additional water from 11 and a middlings recyclesteam 12. The pulped and diluted tar sands are pumped from the sump 10through line 13 into the separation zone 14 which comprises a settlingcell which contains a relatively quiescent body of hot water whichallows for the formation of a bitumen froth which rises to the cell topand is withdrawn via line and a sand tailings layer which settles to thebottom to be Withdrawn through line 16. An aqueous middlings layerbetween the froth and tailings layer contains silt and clay and somebitumen which failed to form froth. Since suflicient clay is not removedin the sand tailings withdrawn from the bottom of the separation cellthrough 16 in order to prevent the buildup of clay in the system it isnecessary to continually remove some of the middlings layer and supplyenough water in the conditioning operations to compensate for that soremoved. The rate at which the middlings need to be removed from thesystem depends upon the content of clay and silt present in the tarsands feed and this rate varies as the content of these fines varies asdetermined per the present invention. If the clay and silt content isallowed to build up too high in the system effective separation will nolonger occur and the process will become inoperative. This is avoided byregulating the recycling and withdrawal of middlings and input of freshwater per the present invention. Even when the separation step isoperating properly the middlings layer withdrawn through line 17 willcontain a substantial amount of bitumen which did not separate. Hencethe middlings layer withdrawn through line 15 is for the purpose ofdescription, herein referred to as oil-rich or bitumen-rich middlings.

The bitumen-rich middlings stream withdrawn from the separator 14through line 17 is sent to a scavenger zone 16 wherein an air flotationoperation is conducted to cause the formation of additional bitumenfroth. The rate of flow of this stream from the separation zone iscontrolled by variable speed pump 19 which is in turn regulated by leadwhich is responsive to the tar sands aluminum content of feed tar sandsas determined in analysis zone 2. For example if the aluminum analysisof the feed tar sands indicates a feed of increased fines content, lead20 increases variable speed pump 19 thereby increasing the flow in line17 to the scavenger zone 18. Increased flow in the scavenger cell 18lowers the interface level between the middlings and froth in separationzone 14. The lowering of the interface level actuates float valve 20which by means of lead 21 opens valve 22 thus increasing the flow offresh water addition to sump 10 via line 11. Increased water flowthrough 11 results in increased water content in the diluted pulppassing from the sump 10 through line 13 to the separation cell 14. Flowthrough valve 23 is decreased via lead 24 which responds to the increasein water in the diluted pulp thereby resulting in a reduction in theamount of middlings recycle diluting the separation cell feed via 12.The net effect of this is an increase in the proportion of fresh Waterin the separation cell 14 so that a constant middlings density ismaintained with the introduction of the high clay containing tar sandsfeed which was analyzed in zone 2. correspondingly if the analysis ofaluminum conducted in zone 2 indicates tar sands feed of decreased claycontent, lead 20 decreases the variable speed pump 19 thereby decreasingthe flow in line 17 to scavenger cell 18. Decreased flow to thescavenger cell raises the interface level in the separation cell 14. Araising of the interface level actuates float valve 20 which by means oflead 21 closes valve 22 thus decreasing the flow of fresh water additionto the sump via line 11. Decreased water flow through line 11 results indecreased water content in the diluted pulp passing from the sump 10through line 13 to the separation cell 14. Flow through valve 23 isincreased via lead 24 which responds to the decrease in water in thediluted pulp in 13 thereby resulting in an increase in the amount ofmiddlings recycle diluting the separation cell feed. Thus the proportionof fresh water in the separation cell 14 is decreased to accommodate thetar sands of decreased fines content so as to maintain a constantmiddlings viscosity in the separation cell. This viscosity can rangebetween 0.4 to 5.7 centipoises, preferably 1 to 2 centipoises.

Following the process further, in the scavenger zone 18 an air flotationis conducted by any of the air flotation 6 procedures conventionallyutilized in processing of ores. The air causes the formation ofadditional bitumen froth which passes from the scavenger zone 18 throughline 25 to a froth settler zone 26. A bitumen-lean middlings stream isremoved and discarded from the bottom of the scavenger zone 18 via line27.

In the settler zone 26 the scavenger froth forms into a lower layer ofsettler tailings which is withdrawn and recycled via line 28- to bemixed with bitumen-rich middlings for feed to the scavenger zone 18 vialine 17. In the settler zone an upper layer of upgraded bitumen frothforms above the tailings and is withdrawn through line 29 and is mixedwith primary froth in line 15. The combined froths are at a temperatureof about F. They are heated with steam and diluted with sufiicientnaphtha or other diluent from 30 to reduce the viscosity of the bitumenfor centrifuging in zone 31 to produce a bitumen product 32 suitable forfurther processing.

What is claimed is:

1. In a hot water process for separating bitumen from bituminous tarsands which comprises forming a mixture of water and said tar sands;passing the mixture to a process separation zone to form an upperbitumen froth layer, a lower sand tailings layer and a middlings layercomprising water, mineral and bitumen and separately removing saidlayers from the said separation zone, the improvement which comprises:

(a) determining the aluminum content of said tar sands; and

(b) regulating the amount of water used to form said mixture byincreasing said amount of water with higher aluminum content anddecreasing said amount of water with lower aluminum content so thatoptimum conditions are maintained for forming bitumen froth in saidseparation zone.

2. The process of claim 1 in which step (a) of the improvement comprisesrendering a sample of said tar sands radioactive by neutron irradiation;recording emissions from said radioactive sample; and analyzing saidemissions to determine the aluminum content of said sample.

3. The process of claim 1 in which step (b) comprises regulating theamount of water used to form said mixture by increasing said amount ofwater with higher aluminum content and decreasing said amount of waterwith lower aluminum content to maintain the viscosity of said middlingslayer in the range of about 0.4 to 5.7 centipoises.

4. The process of claim 1 in which step (b) comprises regulating theamount of water used to form said mixture by increasing said amount ofwater with higher aluminum content and decreasing said amount of waterwith lower aluminum content to maintain the viscosity of said middlingslayer in the range of about 1 to 2 centipoises.

5. A method for determining the processability of bituminous tar sandswhich comprises rendering said tar sands radioactive by neutronirradiation, recording emissions from said radioactive sands; andanalyzing said emissions to determine the aluminum content of said sandsand hence the clay content and ease of processability of said sands.

6. The process of claim 1 in which a monovalent alkaline reagent isadded to said mixture of water and tar sands to maintain the pH of saidmiddlings layer within the range of 7.5 to 9.0.

7. The process of claim 6 which additionally comprises regulating theamount of monovalent alkaline reagent added by increasing said amount ofreagent with higher aluminum content and decreasing said amount ofreagent with lower aluminum content to maintain the pH of said middlingslayer within the range of 7.5 to 9.0.

8. In a system for conducting a hot water process for treating tar sandscomprising a conditioning drum, a separation cell, a first line forsupplying tar sands pulp from said conditioning drum to said separationcell, a second line for introducing hot water into tar sands pulp insaid first line, a third line for withdrawing a bitumen froth productfrom said cell, a fourth line for withdrawing a sand tailings layer fromsaid cell, a fifth line for withdrawing a middlings portion from saidcell, a sixth line for recycling a middlings portion from said cell tobe mixed with said tar sand pulp prior to discharge into said cell; theimprovement which comprises:

(a) a tar sands analysis means for determining feed tar sands aluminumcontent and hence said sands clay content and (b) regulating meanscontrollably attached to said fifth line and responsively connected tosaid analysis means to increase the flow of middlings withdrawn via saidfifth line when said feed tar sands are analyzed to have higher claycontents and to decrease the flow of middlings withdrawn via said fifthline when said feed tar sands are analyzed to have lower clay contents;

(c) regulating means operating in response to said middlings withdrawnin said fifth line and connected to said second line to control the hotWater introduced to the bituminous tar sands pulp via said second line;and

(d) regulating means operating in response to said hot waterincorporated in said second line and connected to said sixth line tocontrol the middlings portion recycled to the bituminous tar sands pulpvia said second line.

9. The system of claim 8 in which said tar sands analysis means (a)comprises a conveyor for moving tar sands through an analysis zone, asource of fast neutrons positioned to irradiate tar sands on saidconveyor to artificially radio-activate said tar sands, a radiationmeasuring device positioned so as to measure energy emissions from saidradio-active tar sands, and a recording device for recording saidmeasured emissions for analysis for de- 8 termining aluminum content ofsaid tar sands according to recorded emissions characteristic of saidaluminum.

10. In a hot water process for treating bituminous tar sands whichcomprises forming a pulp of feed bituminous tar sands with a minoramount of water in a pulping zone, removing pulp therefrom and mixingthe same with hot water and a hereinafter specified recycle stream in adilution zone, passing the mixture into a separation zone, settling themixture in the separation zone to form an upper bitumen layer, amiddlings layer comprising water, clay and bitumen, and a sand tailingslayer, removing a first stream of middlings layer from the separationzone and passing it to the dilution zone as the aforesaid recyclestream, passing a second stream of middlings layer to a scavenger zoneand therein recovering an additional amount of bitumen froth, andregulating the rate of passage of said second stream to the scavengerzone so as to regulate and maintain the viscosity of said middlingslayer within the range of about 0.4 to 5.7 centipoises, the improvementto the regulating step which comprises: measuring the aluminum contentof feed bituminous tar sands and determining sand clay content thereby;and regulating the rate of passage of said second stream to saidscavenger zone according to said measured aluminum content.

References Cited UNITED STATES PATENTS 3,273,967 9/1966 Wilson 232303,401,110 9/1968 Floyd et a1. 208-11 3,421,868 1/1969 Feldman 20811CURTIS R. DAVIS, Primary Examiner US. Cl. X.R.

